The technique of the semiconductor integrated circuit in a package having a plurality of leads located on a surface of a semiconductor chip or substrate, is sometimes called as "lead-on-chip" or "lead-over-chip" (LOC) technology. This type of technology has been discussed in several references, such as:
U.S. Pat. No. 4,916,519 (Ward) Issued Apr. 10, 1990 PA1 U.S. Pat. No. 5,068,712 (Murakami et al.) Issued Nov. 26, 1991 (corresponding to Japanese Kokai H2-246125) PA1 U.S. Pat. No. 5,115,298 (Loh) Issued May 19, 1992.
In an integrated circuit using an LOC technology or in an LOC IC package, the bond pads of the integrated circuit may be positioned in the center of the chip, extending lengthwise. Commonly, the portions of the lead frame which provide power to the chip are formed as long "bus bars" extending the length of the chip on either side of the bond pads. Bond wires are attached connecting the bus bars to the appropriate bond pads using well known techniques such as ball bonding. The lead fingers for carrying the signals to the chip extend from the outside of the chip to the surface of the chip next to the bus bars. Bond wires are attached from these leads over the bus bars to the appropriate bond pads. To securely attach the portion of the lead frame where the bond wires are attached, a double sided adhesive tape is normally used to firmly attach the leadframe to a surface of a semiconductor chip. In addition, an insulative material may be applied to the surface of the bus bars, except where the bond wires are attached to the bus bar, to avoid shorting of the signal lead bond wires to the bus bars.
The lead frame usually includes support ties extending the length of the chip and which extend beyond the ends of the package during the mold injection process. These support ties provide mechanical support to the lead frame and the chip, onto which the lead frame is attached, during the mold injection process and during the lead trim and form process. Often, the support ties are formed integrally with the bus bars on the lead frame. The prior art support ties in prior art may cause warpage after the mold injection process due to the different expansion coefficients of the lead frame, the chip and the mold compound.